This is good advice for all types of email; especially work email. When an email really does need lots of detail, I’ve made a habit of always including a BLUF, or “bottom line up front” - kind of like a TL;DR but more focused on identifying the key things I want the reader to know if that’s the only paragraph they read. I also try to structure and label my emails to make it obvious which parts are “please read all of…
I find an explicitly identified "BLUF" section to be annoying. I can read. If you want to put the most important information or request up front, just do that.
I do use section headings later in long emails to help visually break up the content and help the reader skim/find what they’re looking for.
It would be annoying to begin every email with something labeled BLUF. Although I personally wouldn’t care if it would help more people actually put the bottom line up front.